The present invention relates to a device for measuring the radiation from an object by means of an optical system, said system comprising scanning means for scanning the image space with at least one refracting rotating prism.
Such scanning devices are known. For example, U.S. Pat. No. 3,253,498 describes a scanning device with a rotating prism, which prism scans in one dimension, the patent further stating that scanning in another dimension can be accomplished by means of a tilting mirror.
U.S. Pat. No. 3,617,106 describes a device which comprises two prisms, having their axes orthogonal to each other, said prisms, when rotating, scan an object in two dimensions.
As a rule, the detector in such a system may view a reference radiation source at periodic intervals in time. Such a reference radiation source may then be arranged in such a way that a so-called chopper part of the time reflects said reference radiation source towards the detector. The chopper is further adjusted so as to let radiation from the scanned object pass therethrough another part of the time. When using a detector with a stabilized temperature, the detector may serve as a reference radiation source by being reflected in the chopper and thus being reprojected on itself, all of which is described in U.S. Pat. No. 3,392,282.